4,5-dichloro-6-ethylpyrimidine is a valuable intermediate product for the production of 4-amino-5-chloro-6-ethylpyrimidines, which exhibit insecticidal, acaricidal and fungicidal properties (European Published Pat. application No. 0264217). Previously known processes for the production of 4,5-dichloro-6-alkyl pyrimidines start from the corresponding 4-hydroxy-6-alkyl pyrimidines, which are first converted with elementary chlorine or a chlorine-carrying agent, such as, N-chlorosuccinimide into the 5-chloro-4-hydroxy-6-alkyl pyrimidines (Japanese Published Pat. application No. 222070/83). The latter is then converted with phosphoryl chloride or another inorganic acid chloride into the 4,5-dichloro compounds. It is true that this process in itself can be performed with good yield and is also suitable for industrial scale application, but the drawback is that the required 4-hydroxy-6-alkyl pyrimidines are only poorly accessible. Their synthesis usually starts from the corresponding 2-thio-6-alkyluracil, which is desulfurized with Raney nickel. It is true that the 2-thio-6-alkyl uracils are easy to produce from the corresponding 3-oxocarboxylic acid esters and thiourea (H.M. Foster and H.R. Snyder, Org. Synth., Coll. Vol. IV, 638), but the desulfurization with Raney nickel is not practical for an industrial process.